1. Field of the Invention
The present invention relates to an intramedullary nail used for an intramedullary nailing procedure.
2. Description of the Related Art
The intramedullary nail is mainly used for treating a fracture of the proximal portion of the femur such as an intertrochanteric fracture or a subtrochanteric fracture by pulling the proximal bone portion, separated from the femur by the fracture, to the femur to compress and fix them.
The intramedullary nail includes a nail member inserted into the femur from one end thereof, and a lag screw extending through the nail member and connected to the bone portion separated by the fracture. The lag screw includes engaging means for engaging the separated bone portion at the forward end thereof, and is fixedly supported on the nail member by a set screw inserted into a threaded hole formed in the outer end of the nail member. The nail member is formed with a through hole extending diagonally across the proximal portion thereof so that the forward end of the lag screw inserted into the through hole may be screwed into the bone portion separated by fracture such as the caput of bone positioned at a diagonally upward side.
In the treatment of the fractured proximal portion of the femur, the first step is to insert the nail member in the proximal end of the femur and install it in the medullary cavity thereof. Then, a locking screw can be inserted, if necessary, such that it extends across the medullary cavity and the distal portion of the nail member thereby fixing the nail member at a predetermined position in the femur. As the next step, the engaging means (threaded portion) at the forward end of the lag screw is passed through the through hole of the nail member into the portion of the caput of bone positioned more proximal than the fractured portion thereby to secure the separated caput to the lag screw. After that, the separated caput of the femur is pulled by the lag screw in such a manner as to press the separated caput against the main portion of the femur. When the caput of the femur comes to be positioned adjacent to the main portion thereof, the set screw is inserted into a threaded fixing hole of the nail member so that the forward end of the set screw engages the peripheral surface of the lag screw thereby to secure the lag screw to the nail member.
However, the separated portion of the bone such as the fractured caput, which is secured only to a single bone connector such as a lag screw, is liable to rotate about the bone connector. The rotation of the separated bone portion hinders the separated bone portion from being coapted to the main portion of the bone. Therefore, this can result in a problem that the healing time of the fracture is increased or that the fracture line is displaced before the separated bone portion is coapted to the main portion. In the case where the degree of rotation is high, the muscle surrounding the separated portion of the bone such as the caput may be damaged.
In order to prevent such a rotation of a separated bone portion, it is required to connect the separated bone portion of the femur and the main portion thereof by additionally providing an auxiliary connector extending across the nail member to the separated bone portion. However, the auxiliary connector cannot pass across through the nail member because of the presence of a set screw extending longitudinally inside of the nail member from one end thereof for securing the bone connector to the nail member.
Accordingly, it is an object of the present invention to obviate the problem in the prior art described above to provide an intramedullary nail allowing a bone connector and an auxiliary connector to be inserted into a nail member for preventing the rotation of a bone portion separated from a main portion of a femur by fracture and located on the proximal side of the fractured portion, thereby to promote the healing of the fractured portion.
In order to achieve the object described above, in accordance with a first aspect of the present invention, there is provided an intramedullary nail which includes a bone connector for connecting a bone portion separated from a main portion of a bone by fracture to the main portion, the bone connector extending through the main portion and secured in the separated bone portion; a nail member installed in the main portion of the bone for fixing the bone connector to the main portion, the bone connector extending through the nail member; a set screw inserted into an outer end of the nail member for securing the bone connector in the nail member; an auxiliary connector extending through the nail member between the bone connector and the set screw; and a spacer for transmitting a clamping force from the set screw to the bone connector thereby to clamp the bone connector.
In accordance with a second aspect of the present invention, there is provided an intramedullary nail which includes a bone connector for connecting a bone portion separated from a main portion of a femur by fracture to the main portion, the bone connector extending through the main portion and secured in the separated bone portion; a nail member installed in the main portion of the femur for fixing the bone connector to the main portion, the bone connector slidably inserted through the nail member; a set screw inserted into a set hole for securing the bone connector in the nail member, the set hole formed in an outer end of the nail member and extending longitudinally of the nail member; an auxiliary connector extending through the nail member between the bone connector and the set screw; and a spacer for transmitting a clamping force from the set screw to the bone connector without interfering with the auxiliary connector, thereby to clamp the bone connector.
In accordance with a third aspect of the present invention, there is provided an intramedullary nail which includes a bone connector for connecting a bone portion separated from a main portion of a bone by fracture to the main portion, the bone connector extending through the main portion and secured in the separated bone portion; a nail member installed in the main portion of the bone for fixing the bone connector to the main portion, the bone connector extending through the nail member; a set screw inserted into an outer end of the nail member for securing the bone connector in the nail member; and an auxiliary connector extending through the nail member and arranged in a position where the auxiliary connector is free from the set screw.
In the intramedullary nail described above, the spacer includes two legs extending in spaced relation with each other, and the auxiliary connector extends through the nail member between the two legs. Preferably, the bone connector has grooves formed on a peripheral surface thereof for the two legs of the spacer to engage.
In the above-mentioned intrammedullary nail, the set screw may include a boss extending toward the spacer, which boss passes through the spacer to engage a groove formed on a peripheral surface of the auxiliary connector.
Since the auxiliary connector extending through the nail member between the bone connector and the set screw is provided and the spacer for transmitting the clamping force is interposed between the set screw and the bone connector, the auxiliary connector extending to the separated bone portion through the nail member prevents the rotation of the separated bone portion. Also, the clamping force of the set screw inserted to the outer end of the nail member is transmitted to the bone connector over the auxiliary connector via the spacer, thereby permitting the bone connector to be secured in the nail member.